Linear actuator systems are used in various applications and typically comprise one or more electro-mechanical actuators operated by a DC motor, a controller and a power supply. The power supply is a conventional power supply based on a transformer and a rectifier in the form of a rectifier bridge and a capacitor for smoothing the voltage as such power supplies are very robust and reliable. However such power supplies have the disadvantage that they are heavy and voluminous and require a relatively large amount of materials and that the efficiency is about 50-60% at full load.
On the other hand, a switch mode power supply typically has a higher efficiency, typically 80-90% at full load, while the amount of required material is less than a conventional power supply as described above. One of the main reasons for reducing the amount of material is due to the magnetic circuit. In a traditional power supply the step down transformer operates at a frequency of 50 Hz, whereas a switch mode power supply has a magnetic circuit operating at around 30-50 kHz, thus allowing the size of the magnetic circuit to be reduced.
Switch mode power supplies are as such well known and some may refer to known topologies such as: Fly Back, Boost, Buck, SEPIC and Forward, with Fly Back as the most common occurrence. These prior art switch mode power supplies each have their advantages and disadvantages. However, despite the advantages such as the high efficiency switch mode power supplies have for various reasons not gained footing within linear actuator systems, which requires robust and reliable power supplies with a relative high output.
It is noted that the said actuator system is used for various purposes within the industry (machines and process plants, agricultural and construction equipment etc.), furniture (adjustable beds, recliners etc.), hospital and care furniture (hospital and care beds, treatment couches and chairs, patient lifts, wheelchairs etc.), office furniture (hand/stand-up desks etc.), energy (solar tracking etc.) just to mention some field of applications.
As for many other field of applications requiring a direct current power supply, there is a demand for systems which can operate worldwide without having to change components or mechanical switches in respect of the actual voltage level such as 110 VAC/230 VAC at a given location.